Where talking about character who is basically commander status for reason. Who has lower bounty than jack right now. We saw what happened when she was fighting against ulti. Without big mom interference Nami would likely be dead. During whole cake island we did see nami struggle against smoothie. Even with Zeus I don’t think it would be enough. For Yamato make most sense for her fight her since both them incredibly strong and having incredible durability they are both use to fighting.